Featured Image Credit: BILL CURTSINGER, NATIONAL GEOGRAPHIC CREATIVE
By: Jessica Kittel
For everyone that likes to take discreet catnaps at their desk or in class, turns out your spirit animal might just be the harbor porpoise.
New research published by Andrew Wright, from the University of Canterbury, suggests that harbor porpoises doze off while diving.
During his Ph.D. research in waters just off of Denmark, Wright tracked harbor porpoise diving behavior using behavioral loggers. These behavioral loggers provided some interesting data that led to Wright discovering a whole new type of diving behavior. These dives were slow, utilized little energy, and had few echolocation clicks.
It’s a relatively well-known piece of information that cetaceans only use half of their brains when they sleep. This is called unihemispheric slow wave sleep (USWS) and has been seen in all members of cetacea. Unlike us, cetaceans are conscious breathers meaning they need to consciously rise to the surface intermittently to take a breath. If a dolphin or whale were to be knocked unconscious they would likely die due to the fact that would not breath, even if they were at the surface.
In order to make sure they come up for air while sleeping, they never completely turn their brains off. They will rest with one half of their brain switched off then the next time they sleep they will switch off the opposite side of their brain. The half of the brain that isn’t resting tells them to surface every now and then and take a breath.
This new information suggests that not only do they sleep while swimming at the surface, but also during dives. This information does bring into question whether sleeping at depth could make these porpoises more likely to become entangled in fishing nets. Wright suggests that if fishermen do not put nets at the depths that porpoises sleep at they may be able to reduce entanglement rates.